Injection cylinder for metal casting



United States Inventors Appl. No.

Filed Patented Assignee Conrad A. Parlanti Berkeley, California; GeorgeH. Fashi'eiiew, St. Charles; Dort Fauntleroy, Geneva, iiiinois INJECTIONCYLINDER FOR METAL CASTING 1 Claim, 1 Drawing Fig.

US. Cl 164/312 Int. Cl 322d 17/08 Field ofSeareh 164/312,

314, 315. l 13, 303-305, P.V. (Die Cast Dig):

l8/30(HB). 36m; 249/80 {56] References Cited UNlTED STATES PATENTS2,244,816 6/1941 Von Lynn 164/3 2,610.372 9/1952 Schroeder ....L64/P.Die Cast 2,947,045 8/1960 Goldhamer. 164/303 3,224,860 12/1965 Stinnes249/80X Primary Examiner-Robert D. Baldwin Attorney- Parker. Carter andMarkey ABSTRACT: In the die casting of molten metal, for example ferrousor high-temperature metals, the molten metal is introduced into aninjection cylinder and the metal is normally moved by a reciprocatingplunger from the injection cylinder into the die cavity. Theintroduction of molten metal into the injection cylinder can causetemperature distortion of the cylinder walls and thus permit leakage ofthe molten metal around the plunger which is pushing the metal into thedie cavity. The temperature distortion of the cylinder wall isnonlinear. To prevent such distortion, means are provided to cool theinjection cylinder, with the cooling being nonuniform in accordance withthe temperature increase of various areas of the cylinder caused by theintroduction of the molten metal.

INJECTIONCYLINDER FOR METAL CASTING SUMMARY OF THE iNvENrioN Thisinvention relates to a die casting method and apparatus in which the diecasting injection cylinder is cooled to prevent temperature distortionofithe cylinder walls.

A primary purpose is an apparatus of the type described in which thecooling means provides increased heat radiating areas at the exterior ofthe injection cylinder.

Another purpose is-a reliably operable injection cylinder for hightemperature moltenvmetals, including a plurality of heat radiating finsextending outwardly from the injection cylinder surface to providecooling of the cylinder and thus prevent temperature distortion.

Another purpose is an=improved method of die casting high temperaturemolten metals including means for preventing temperature distortion ofthe injection cylinder wall. Another purpose is an improved method ofdie casting high temperature molten metal in which the injectioncylinder is selectively cooled to prevent nonlinear temperaturedistortion.

The invention herein described was made in the course of or under acontract with the Department of the AirForce.

Other purposes will appear in the ensuing specification, drawing andclaims. 1

BRIEF DESCRIPTION OF THE DRAWING The invention is illustrateddiagrammatically in the attached axial section through an injectioncylinder of the type described.

DESCRIPTION OF THE PREFERRED EMBODIMENT sure zone 18 which is defined bya sleeve or shell 20. Outside of the sleeve or shell 20is a secondsleeve 22, which may be substantially thicker in radial extent than thesleeve 20. The sleeve 22 may have a plurality of heat radiating finsextending outwardly therefrom. The fins will be described in detailhereinafter. The injection cylinder 16 may include a molten metal feedpassage 24 and a reciprocating plunger 26 which moves back and forthwithin the chamber or pressure zone 18.

In some applications the injection cylinder may be surrounded by a cowlor the like 28 which is effective to enclose the entire cylinder, aswill be described hereinafter.

The inner sleeve or shell 20 is preferably formed of a high heatresistance metal such as molybdenum or any of the high resistant steelsor nickel chromium alloys which have a good rate of heat resistance andalso good heat conductivity. This is important in order to conduct heatrapidly to the second laminate which then radiates heat into thesurrounding area.

Normally the inner shell 20 will be relatively .thin in radialthickness, for example on the order of one-quarter inch to one-halfinch. The outer shell 22, which may be formed of copper, aluminum or oneof their alloys, is of sufficient thickness so that it will .be able towithstand the mechanical demands made by the high internal pressuresnecessary to force the molten metal into the die cavity. For example,the pressure within the chamber 20 can range from 4500 psi. to 20,000psi. at working temperatures in the range of 800F. to 1 100F.

When molten metal is introduced into the chamber 18, the wall 20 will beheated by the molten metal, but on a nonuniform or nonlinear basis.There is a zone 30, adjacent the mold 10, in which the highesttemperatures will be reached during the die casting operation. There isa second zone 32, adjacent the end zone 30, in which the temperaturesare sub stantially lower. There is a third zone 34, which is adjacentthe molten metal feed opening 24, which again will have substantiallyhigh temperatures in the end zone 30. There is a fourth zone 36 which isgenerally about the plunger in its rest position, in which again thetemperatures will be somewhat the 3 same as the zone 32 andsubstantially; lower than the temperatures in the zones 30 and 34. Inorder to prevent nonlinear distortion it is necessary first to cool theentire injection cylinder, and secondly, to selectively cool theinjection cylinder so that the areas having the greatest temperatureincrease will receive the greatcst cooling effect. The heat radiatingfins formed about the cylinder are thus selectively arranged to providethe greatest cooling effect in the zones 30 and 34. The heat radiatingfins 38 in the zone 30, and the heat radiating fins 40 in the zone 34,are of substantially greater I radial extent than the fins 42 in thezone 32 and the fins 44 in the zone 36. Thus, those areas receiving thegreatesttemperature increase due to the introduction of molten metalinto the chamber 18 will have the greatest heat radiating areas, andthus will receive the greatest cooling.

As an example of the type of temperatures which can be reached withinthe chamber 18 of the molten metal is a ternperature of about l500F. Thetemperatures in the end zone 30 will range from 800F. to 1 100F. In thecenter zone 34 the temperatures will range from 620F. to l060F. Thetemperatures in the cooler zone 32 will range from about 290F. to 590F.and the temperatures in the zone 36 are in the area of 300F.

In some applications it is desirable to provide cooling air about theinjection cylinder. For this purpose, the cowl 28 surrounds theinjectioncylinder and thus provides a defined path for the cooling air.Water cooling may also be provided, however, it has been found to bemore advantageous to provide air cooling due to the opening of the feedpassage 24 in the space adjacent the cooling area.

The use, operation and function of the invention are as follows:

The introduction of molten metal, for example at a tem perature of aboutl500F., into a cold cylinder will cause expansion of the cylinder walls,particularly uneven expansion on the receiving side of the wall. Thepiston or plunger 26 will also expand, however, it has less exposed areaat its outer periphery and hence will not expand the same amount as thewalls of the injection cylinder. Thus a clearance will be formed betweenthe periphery of the plunger and the chamber wall 20. This clearancewill permit the molten metal to be squeezed between these surfaces asthe plunger pushes the metal into the mold opening 12. Not only will theloss of metal, due to the clearance between the walls, reduce the amountof metal actually injected into the mold cavity, but such leakage orseepage can cause damage to the die injecting mechanism.

By cooling the injection cylinder, the temperature distortion of thecylinder wall is substantially minimized and to a large extenteliminated. In some applications it may also be desirable to cool theplunger, but this is not necessary in every case. It is important toselectively cool the injection cylinder in accordance with thetemperature increases of the cylinder from the molten metal. Not only isit necessary to minimize temperature distortion of the entire cylinder,but it is necessary to make sure whatever expansion there is in thecylinder wall is uniform, and not nonlinear. For this reason, thoseportions of the injection cylinder which receive the greatesttemperature increase due to the molten metal have heat radiating fins ofgreater radial extent, thus providing greater cooling area.

The makeup of the injection cylinder is important. An inner laminate ofa high heat resistant steel, for example one of the nickel chromiumalloys, or molybdenum, has been found to be satisfactory. Such materialshave a good rate of heat resistance and also good heat conductivity. Theheat resisting inner laminate will resist and contain the heat, and yetby its own rate of heat conduction transfer the heat to the outer shell22 whic'his cast around it. Either aluminum or copper, or one of theiralloys, have been found to be satisfactory for the outer shell 22 andfor the heat radiating fins forming a part thereof.

The details of the mold and the plunger reciprocating mechanism have notbeen shown herein, but such mechanisms are common in the art.

Whereas the preferred form of the invention have been shown anddescribed herein, it should be realized that there are manymodifications,substitutions and alterations thereto,

within the scope of the following claims.

We claim:

1. in a system for die casting molten metal, a mold having an inputopening, an injection cylinder positioned adjacent said mold, anopen'ended chamber in said injection'cylinder in alignment with the moldopening, a plunger reciprocal in said chamber for injecting molten metalfrom the chamber into

